1. Field of the Invention
The present invention relates to light diffusers and to methods for manufacturing the same. In particular, the invention relates to diffusers, which have suitable properties for use in LED lighting applications. The invention also relates to a structure and manufacturing method of these diffuser structures. In addition, the invention relates to materials and methods used to produce the diffusers.
2. Description of Related Art
Light Emitting Diode (LED) typically consists of following parts/components: A semiconductor wafer: where the light emission is produced typically in form of UV light; LED cup wherein the LED wafer is mounted using typically a solder processing, wire-bonding and encapsulation; Encapsulate material wherein phosphorous mixed when considering white light LEDs. The encapsulate material is dispensed onto the LED chip and the cup. The encapsulate material can be for example a transparent silicone or epoxy adhesive. The phosphor what is dispersed into the encapsulate converts short wavelength light (typically blue light) emitted by the LED wafer into white light; LED lens is molded on top of the LED wafer/substrate/encapsulate structure typically using the same encapsulate material than previously used with the phosphorous encapsulant area. The LED lens is used to direct the light certain way from the LED.
The above-described parts/components construct the basic single LED device with high efficiency spot light source. When constructing LED displays, display backlights or lighting units using LED's, typically an additional diffuser film or structure is provided to modify the light emission toward the viewer and particular in the LED lightning unit it is particularly important to remove the spot like phenomena and convert the light source to uniform emitter.
In recent years LED's have gained a lot of attention as a very low power consumption alternative for replacement of the conventional indoor and outdoor lighting. Due to the LED's small size it brings out a lot of different design options to construct the indoor and outdoor light sources. However, when using LED's to replace the conventional light bulbs and fluorescent tube lamps, the requirement is that the properties of the current lamps need to be met example in terms of light intensity and light emission uniformity. A “spot like” LED light emission is not desired. For this reason, one of the main challenges is to be able to create a uniform diffused light from the LED lamps towards the viewer and the ambient and at the same time minimizing the LED amount in a lamp or lighting set. Same time it is important that the light diffusion is minimally impacting to the light efficiency losses of the light system. Furthermore, the diffusion element should be light weight, robust, non-yellowing and withstand cleaning chemicals, high and low environmental temperature conditions and finally should be economical to manufacture in high volumes. Also an ideal diffuser should not be prone for fingerprint soiling.